The present invention relates to a developer replenishing device for a copier, facsimile apparatus, printer or similar electrophotogrpahic image forming apparatus. More particularly, the present invention relates to a develop container storing a developer, i.e., toner or a toner and carrier mixture and removably mounted to the body of the image forming apparatus, and a method of conveying the developer to the developing unit or similar preselected location.
It is common practice with an image forming apparatus to sense the toner content of a developer stored in a developing unit for maintaining it constant. A developer container storing a developer and implemented as, e.g., a bottle or a cartridge is located in or in the vicinity of a unit including the developing unit. The developer is replenished from the developer container to the developing unit either directly or via a toner hopper.
Because the developer is replenished to and consumed by the developing unit, the developer container is replaced at an adequate time. The replacement of the developer container is one of awkward operations to perform. Various implementations have heretofore been proposed to promote easy replacement of the developer container. For example, a toner bottle may be positioned on a support member and automatically opened when the support member is returned to a preselected position. The developer container may be implemented as a flexible sack and set in the developing unit. When the sack in its open position is emptied, it is compressed and left in the apparatus body.
However, the problem with the above toner bottle scheme is that it needs a sophisticated, expensive mechanism and is applicable only to high-class image forming apparatuses. The flexible sack scheme needs an extra space for storing the compressed sacks. Moreover, because toner is replenished into the developing unit due to its own weight when the sack is opened, the sack must be positioned above the developing unit.
The conventional toner container in the form of a hard cartridge or a hard bottle has another problem left unsolved as to disposal after replacement. Specifically, it has been customary for a manufacturer to collect used toner containers form users' stations and recycle, reuse or burn them up. The hard cartridges or bottles are bulky and increase the circulation cost up to collection.
There has been proposed a developer container whose volume can be reduced. With this kind of developer container, however, a developer cannot be stably replenished to the developing unit. Even if the volume of the developer container can be reduced only during transport, the developer is apt to bring about contamination at the time of transfer.
On the other hand, the developer is often conveyed from the developer container to the developing unit by a screw, paddle or similar mechanical auger means. A drawback with the mechanical auger means is that the screw for conveying the developer must be substantially linearly arranged. Therefore, the developer container and developer replenishing device must be constructed integrally with or located in close proximity to the developing unit. As a result, the developer replenishing device is sophisticated and expensive, lowers productivity, obstructs maintenance, and makes it difficult to maintain the property or quality of the toner. In addition, the developer container is difficult to replace.
Japanese Patent Laid-Open Publication No. 7-219329, for example, proposes to convey toner together with air via a flexible tube by use of a screw pump and air feeding means. The screw pump includes a rotor rotatable to move toner, or developer, in the axial direction, and a stator surrounding and contacting the rotor. The air feeding means feeds air under pressure for fluidizing the developer being moved by the screw pump.
The convey system using the above screw pump is capable of surely conveying the developer via the flexible tube and therefore with a simple configuration without regard to the location of a toner storing section or that of a toner collecting section. Further, the compressed air fluidizes the developer for promoting stable conveyance of the developer and frees the developer from mechanical stresses that would bring about blocking or bridging. However, the screw pump essential with this system increases the cost.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 6-59572, 7-306576, 8-211718 and 11-52695 and Japanese Patent No. 2,677,575.